1. Field of the Invention
The present invention relates to a welding wire containing flux used for a gas shielded arc welding of a direct current positive polarity mode with polarity arrangement that the welding wire is biased as a negative electrode and a mother material is biased as a positive electrode. More particularly, the present invention relates to a gas shielded arc welding flux cored wire, with use of which a quantity of sputter generated is small, a good weldability (bead forming inclination) is realized and a weld metal with an excellent toughness is obtained in all the welding positions such as not only a flat welding position but a vertical welding position and the like under application of a welding current in the range of a low current to a medium current, or in a definite manner in the range of 50 to 300 A.
2. Related Prior Art
The applicant has proposed a barium fluoride based flux cored wire, which is added with BaF2 as a fluoride for the purpose to decrease a quantity of sputter by stabilizing arc (Publication of Unexamined Japanese Patent Application No. Hei. 2-55696). The barium fluoride based flux cored wire is used in a direct current positive polarity mode, where a direct current is used in arc welding and a wire is biased as a negative electrode (a mother material is a positive electrode). In the case of this direct current positive polarity mode, a melt drop at the tip end of the wire receives not only an impact force caused by a positive ion but a large reactive force caused by evaporation of BaF2 and the like having a high vapor pressure, so that the melt drop at the tip end of the wire is transformed into smaller melt particles by the result of those forces, whereby a smooth transfer to the mother material is realized. Thus, stabilization of arc and reduction in a quantity of sputter is achieved.
The conventional gas shielded arc welding flux cored wire of a direct current positive polarity mode, which has been proposed, has a feature that the wire comprises BaF2, Al, Mg, Fe, Mn and Si as indispensable components and a quantity of sputter generated is small under application of a low welding current in the range of 100 to 200 A.
However, with the conventional wire in use, there have been problems to be solved, which are 1) reduction in a quantity of sputter, 2) improvement on weldability (ability to realize good shaped bead formation) and 3) improvement on toughness of a weld metal, in all the positions such as a vertical position, a horizontal position, an overhead position, in which molten metal is subject to hanging-down by an influence of the gravitational force, under application of a welding current in the range of a low current to a medium current, or in a definite manner in the range of 50 to 300 A.
It is, accordingly, an object of the present invention to provide a gas shielded arc welding flux cored wire used in a direct current positive polarity mode, with use of which a quantity of sputter generated is small, a good weldability is realized and a weld metal with an excellent toughness is obtained in all the welding positions such as a flat welding position, an overhead welding position and the like under application of a welding current in the range of a low current to a medium current, or in a definite manner in the range of 50 to 300 A.
A first aspect of the present invention is directed to a gas shielded arc welding flux cored wire used in a direct current positive polarity mode, comprising: a steel sheath; and flux with which the steel sheath is filled, wherein the flux contains 0.7 to 3 wt % Al, 0.1 to 1.2 wt % Mg and 1.2 to 5 wt % BaF2, each content being a value in wt % to a total weight of the wire and the sum of a content of Al plus a content of Mg multiplied by 3 being in the range of 1.3 to 5 wt %, a filling ratio of the flux to the total weight of the wire is in the range of 5 to 30 wt %, a total Mn content in the steel sheath and the flux combined is in the range of 0.2 to 1.9 wt % and a total Si content in the steel sheath and the flux combined in the range of 0.001 to 0.9 wt %.
A second aspect of the present invention is directed to a gas shielded arc flux cored wire used in a direct current positive polarity mode, comprising: a steel sheath; and flux with which the steel sheath is filled, wherein the flux contains 0.9 to 2.5 wt % Al, 0.1 to 0.8 wt % Mg and 1.2 to 4 wt % BaF2, each content being a value in wt % to a total weight of the wire and the sum of a content of Al plus a content of Mg multiplied by 3 being in the range of 1.6 to 4 wt %, a filling ratio of the flux to the total weight of the wire is in the range of 7 to 20 wt %, a total Mn content in the steel sheath and the flux combined is in the range of 0.4 to 1.6 wt %, a total Si content in the steel sheath and the flux combined in the range of 0.001 to 0.6 wt %, a total C content in the steel sheath and the flux combined in the range of 0.005 to 0.08 wt %, wherein a ratio of the austenite forming elements to the ferrite forming elements X=(4Ni+7Mn+20C)/(2Al+Si)xe2x89xa70.7, wherein the atomic symbols indicating respective contents of the corresponding elements, and a content of oxygen in a weld metal from the wire is 200 ppm or less.
A third aspect of the present invention is directed to a gas shielded arc flux cored wire used in a direct current positive polarity mode according to any one of the first and second aspects, wherein the flux further contains 0.1 to 3 wt % Ni, the weight % being to the total weight of the wire.
A fourth aspect of the present invention is directed to a gas shielded arc flux cored wire used in a direct current positive polarity mode according to any one of the first to third aspects, wherein the flux further contains 1.5 wt % or less oxides, the weight % being to the total weight of the wire.
With a flux cored wire used in gas shielded arc welding of a direct current positive polarity mode pertaining to the present invention having the above described constitution, a quantity of sputter generated is small, and not only is good weldability realized but a weld metal with an excellent toughness can also be obtained in all the welding positions such as a flat welding position, an overhead welding position and the like can also be attained under application of a welding current in the range of 50 to 300 A, that is in the range of a low current to a medium current.